1. Field of the Invention
The present invention relates to image forming apparatuses such as a copying machine, a facsimile machine, and a printer and a sheet-feeding cassette for feeding a sheet to such image forming apparatuses.
2. Description of the Related Art
An image forming apparatus like those described above is provided with a locking structure which locks a sheet-feeding cassette when the sheet-feeding cassette is set in a cassette accommodating section of the image forming apparatus, and unlocks the sheet-feeding cassette when the sheet-feeding cassette is drawn out of the cassette accommodating section.
As an example of the locking structure, Japanese Patent Unexamined Publication No. 2006-76695 (hereinafter, referred to as “patent document 1”) discloses a known locking structure which is provided with a locking pin in a cassette accommodating section of an image forming apparatus, a pivotal locking lever locked by the locking pin on a side of the sheet-feeding cassette, and a spring for retaining the locking lever to be locked to the locking pin.
According to this locking structure, the locking lever is locked to the locking pin by the spring when the sheet-feeding cassette is set in the cassette accommodating section. The locking lever is pivotally moved apart from the locking pin against the spring by a drawing force, so that the locking structure is unlocked when the sheet-feeding cassette is drawn out of the cassette accommodating section.
Thus, when unlocking is performed with the technology disclosed in the patent document 1, a large amount of force is required which includes a force for drawing the sheet-feeding cassette out of the cassette accommodating section and a force for pivotally moving the locking lever so as to detach the locking lever from the locking pin against the spring. Therefore, room for improvement in operability has been left. Further, there has been a disadvantage that a loud sound occurs when the locking lever is moved back by the spring after the locking lever is detached from the locking pin.
The present invention was made to solve the problems of the conventional technology, and its object is to provide a sheet-feeding cassette and an image forming apparatus capable of performing unlocking without need for a large amount of force and without occurrence of a loud sound.